What does a World War 2 pin that says 'Celer Et Audax' mean?

it literally means sharp and bold/brave

It's also the motto of the 6th Field Artillery:

http://www.tioh.hqda.pentagon.mil/FA/6FieldArtilleryRegiment.htm

The WW 2 "pin" that you have is known as a D.I., short for Distinctive Insignia. It is the unit crest of a particular unit, & worn on the blouse (dress jacket) of the soldier's uniform. The "Heraldry" of this D.I. indicates that it is a cavalry unit, as indicated by the crossed sabers. The rattlesnake indicates that the unit saw service in the southwestern part of the U.S. early in the history of the unit. Tank Destroyer units generally did not have a D.I. for their unit, not all military units had D.I.'s. But there were times when a unit would have their own D.I. "made up," & not ok'ed by the Office of Heraldry, U.S. Army. This may be one of those times, where the 776th T.D. Battalion had their own D.I. made up. Obviously more research is needed.

Richard V. Horrell WW 2 Connections.com

It's not the DI of the 776th TD Btln. That DI can be seen here:Org Support 776

'Celer Et Audax'is the motto of the King's Royal Rifle Company, a British unit. Since the US Tank Destroyer units were often attached to many other units, both US and foreign, and were credited with saving those units bacon many times, your pins could have been given to your grandfather as a gift of appreciation. The site I listed above has a history of the 776th were you can further research the units they may have been attached to.

My dad was in the 894th Tank Destroyer Batallion, and he has a DI from an army Air Force Unit. I wish I had gotten interested in all this when he was still alive to answer questions.

Thanks for the offer but I know all about the 894th. There is an excellent book on the unit's history "Seek, Strike, Destroy, The History of the 894th Tank Destroyer Batallion" by Patrick Chase, which I have. What I don't know is my fathers many stories. I don't know how a GI who spent his entire time in TDs has an Army Air Force Training School DI in with his medals and badges. I would like to know what caused a man who qualified as expert with bayonet, marksman with rifle, and expert with the towed 37mm anti tank gun, to never again pick up a gun. I would like to know the stories behind the pictures he took like the German dive bomber with it's bomb falling through the air to a point that looks to be VERY close to the picture taker.

What further information about the 894th T.D. Batt. do you desire? I have the date & location that the 894th was activated, from where & when they left the U.S., when the 894th landed in England, North Africa & Italy. I have the list of campaigns the 894th was in, along with the date the unit was de-activated.

Richard V. Horrell WW 2 Connections.com

Celer et Audax was the motto of the British 60th Regiment (Royal Americans) formed in 1755 in North America. Its 1st Battalion was commanded by the renowned Light Infantry expert Colonel Henry Bouquet. After the American War of Independence the 60th Regiment moved to Canada. The 5th Battalion 60th Regiment, formed in 1798, were green uniformed riflemen who served with distinction in the Napoleonic Wars in Portugal and Spain in the early 1800s. Their first commander was Colonel Francis de Rottenburgh who wrote the British Army Light Infantry training manual of that period. Many of his ideas can be seen to be the forerunners of modern infantry concepts.

After the Napoleonic Wars the 60th Regiment moved to Britain and were re-titled the Kings Royal Rifle Corps. Today they have been further amalgamated and form part of the Royal Green Jackets.

The regiment has prided itself on being experts on light infantry skirmisher tactics, evolving from their first experiences of emulating North American Woodland Indian fighting methods 250 years ago. There has been a tradition of a number of American volunteers serving in this British Army unit which continued throughout the First and Second World Wars, even prior to the United States entering both those wars. I am aware that relatively recently, possibly even today, such links have continued with formal exchange postings with the United States Army.

The pin in question could easily be linked to such a connection.

Rod MacArthur(former British Army Lieutenant Colonel)